An industrial sewing machine is typically controlled by means of a pivotal foot pedal operated switch depressed by the machine operator. Pressure applied in the toe direction actuates the motor and controls its speed--the greater the pressure, the faster the motor and sewing machine will run. Pressure applied in the heel direction actuates auxiliary functions, such as lifting of the presser foot and trimming the sewing thread end.
Each sewing machine, dependent on its manufacturer, utilizes a motor which requires a particular control device in terms of the operating signals generated for each function. Each motor typically comes equipped with its own unique microprocessor control. A control device suited to the motor's microprocessor is normally purchased with a sewing machine and its motor and becomes a permanent component of the associated sewing system. There are a number of sewing machine motors in use, including models made or sold under the names of Efka, Mitsubishi, Panasonic, Singer, Juki, Brother, Clinton and others.
Traditionally, sewing machine operators spend the entire work shift seated in front of their machines without a substantial change in position. This type of working habit has recently become recognized as the cause of several physical problems for long term sewing machine operators, among them back strain, circulatory problems and carpal tunnel syndrome. In recent industrial studies, significant change in the working position of the operator has been shown to help alleviate the effects of these physical problems as well as help increase operator efficiency. The ergonomic answer to the constant sitting situation is to raise the sewing machine table higher at times and allow the operator to stand while working. This stand and sit working position ability is done at the option of the operator and also serves to reduce fatigue.
There has been found to be a drawback to this solution of raising the table in that the speed controller foot pedal which is adapted and positioned for use by an operator in a seated posture is not well suited to use when the operator is standing. If the operator attempts to use the same controller standing as sitting, even if the foot controller is placed in an accessible position, the operator is forced to not put weight on the controller foot, thereby effectively standing on one foot. A one-foot standing postion cannot be maintained for long periods of time.
A solution to the problem of using a speed controller while sitting or standing is to use two separate speed controllers, one adapted for standing and one adapted for sitting. Physically, this is workable, but it has required the operator or the mechanic to electrically connect and disconnect the controllers at appropriate times, since the machine will not function properly with two simultaneous input speed control cords attached. The process of connecting and disconnecting the controllers tends to increase the time of changing from the sitting to the standing posture, and thereby makes the change less helpful and less efficient.
Therefore, a main objective of the present invention is to provide a sewing machine motor speed control device which allows operation of a sewing machine with the operator being in either a sitting or a standing posture.
An additional objective of the invention is to provide a motor speed control apparatus which is capable of interconnecting two foot pedal controllers to one motor.
A further objective of the invention is to provide a motor speed control apparatus which is useful with different brands of sewing machine motors.
Another objective of the invention is to provide a motor speed control apparatus which can be left connected electrically and physically without requiring resetting.
These and other objectives will become apparent to those skilled in the art as the disclosure is read and understood.